__________ is used as biofertillizer :

Options

A. Azolla
B. Marsilea
C. Equisetum
D. Salvinia

Answer

**Step-by-Step Solution:**

1. **Understanding Biofertilizers**: Biofertilizers are substances that contain living microorganisms which promote plant growth by increasing the supply or availability of primary nutrients to the host plant.

2. **Identifying the Options**: The question provides four options, one of which is Azolla. We need to determine which of these options is recognized as a biofertilizer.

3. **Exploring Azolla**: Azolla is a water fern that has a symbiotic relationship with blue-green algae (cyanobacteria). This relationship allows Azolla to fix atmospheric nitrogen, converting it into ammonia, which is then available to plants.

4. **Understanding Nitrogen Fixation**: Nitrogen fixation is a process where atmospheric nitrogen (N2) is converted into a form that plants can absorb and utilize. This is crucial for plant growth as nitrogen is a key nutrient.

5. **Comparing Other Options**: The other options provided (which are not specified in the question) are likely members of the pteridophyte group but do not have the ability to form a symbiotic relationship with nitrogen-fixing bacteria.

6. **Conclusion**: Since Azolla is the only option that demonstrates a symbiotic relationship with cyanobacteria and is capable of nitrogen fixation, it is classified as a biofertilizer.

**Final Answer**: Azolla is used as a biofertilizer.

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